Eagle737 - I think you answered your own question.

"Retract the landing gear after a positive rate of climb is indicated on the altimeter."

That means the altimeter.

If Boeing had wanted you to measure positive rate of climb on another instrument, they would have stipulated that - or omitted the altimeter from the instruction.

Verifying it off all the other instruments is a good idea... but I can't help wonder why so many have a problem with just calling it off the altimeter as stipulated.

...only true words in this thread so far:zzz:

Hello! A-320 a/c. In my company SOP the positive rate of climb is when radio alt, vertical rate and pressure alt are going up.
Let's imagine a litle bit. You've just airbone so the first signe of the positive rate that you can see is radio alt changes (one second of time). Second, the most obvious, sign is VSI changes (another second). Third, the pressure alt changes, it is one more second. Next we confirm:"posituve climb" and PF order:"Gear up". Then PNF moves the gear leather up.
Totally we have ay least 5 seconds from lifting up to the begining of gear up preses. With the average speed is equal to ~500 f/m we will be at 41' above ground. so you don't need to worry about to early gear retraction.

Con respecto!

Isn't this alot of text for something I thik most of us do instinctively?

Youv'e gone through Vr and the nose is pointing skyward, the hairdryers are still operating and the seat of your pants and your eyes are saying you are climbing so you back it up with the relevant instrumentation your SOP's have indicated and call 'positive rate'